Sensitized silver halide emulsions



Patented Nov. l10,. 1936 SENSITIZED SILVER HALIDE EMULSIONS Wilhelm Schneider, Dessau in Anhalt, Germany,

assignor to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York Application March 16, 1933, Serial No. 661,187 In Germany March 18, 1932 11 Claims.

My present invention relates to sensitizing of photographic emulsions.

One of its objects is to provide such an emulsion the sensitivity of which is raised over the range of wave lengths to which the emulsion is normally sensitive. Further objects will be seen from the detailed specification following hereafter. Reference is made to the accompanying drawing showing some spectograms of emulsions sensitized according to applicants present invention.

I have found that dyestufs of the polymethine series which are substituted at, the central carbon atom of the polymethine chain by a thlenyl group'are powerful sensitizers for photographic silver halide emulsions and particularly for silver halide gelatin emulsions.

The manufacture of these dyestuffs has been described in my copending application Ser. No. 661,185 filed March 16, 1933. I'hey correspond, for instance, with the following formula wherein R1 stands for alkyl or aryl, R2 stands for vinylene, phenylene, naphthylene, and so on, Ra stands for thienyl or a substitutedthienyl,Ystands for oxygen, sulfur, selenium,` X stands for Cl, Br, I, SOiCHs, C104 or another acid radical.

The dyes are obtainable according to the desired solubility in form of the bromide, iodide, perchlorate etc. and are used in a quantity, such as is usual for the known sensitizing dyes. This quantity may amount to about l5,to 30 milligrams per kilo of emulsion ready for being cast which contains about 9 per cent of gelatin, 4.5 per cent of silver halide and the rest water. However, the invention is not limited to the quantities Just indicated and the most suitable amount can be found in each case by a few comparative experiments. The dyes may be added to the emulsion in form' of solutions. Suitable solvents are the alcohols, for instance, methyl or ethyl alcohol which may be used anhydrous or diluted withwater. The dyes are applied to the emulsion during any stage of its production; however, they are preferably added to the ilnished emulsion before casting.

The dyes may likewise be incorporated in the emulsion, by coating or bathing the ilnished photographic material in a bath in which the dye is dissolved. Such a treatment may be as follows z-The photographic material to be sensitized is bathed in a solution containing l milligram of bis- [3-.ethy1-naphtho-2.l'4.5thiazole(2) l thienyl-trimethine-cyanine bromide in 50 to 100 cc. of an aqueous solution of methanol of 50 per cent strength. The material is then dried, whereupon it is ready for use.

The incorporation of the sensitizer by coating may be effected by applying to the emulsion which has been cast but is not yet dry a solution of the sensitizer of suitable concentration by nreans of a coating roller. The concentration depends, of course, on the speed of the coating roller. peripheral speed of the coating roller is 20 cm. per second a solution containing 1 milligram oi Itthe sensitizer in about 100 cc. of an aqueous solution of methanol of 50 per cent strength may do.

The accompanying drawing shows some spectrograms of emulsions sensitized according to applicants present invention in comparison with an unsensitized emulsion.`

No. 1 shows the spectrogram of a silverbromlde emulsion containing about 4 per cent of silver iodide.

No. 2 shows a spectrogram of the same emulsion sensitized with bis-[3-ethyl-benzoxazole-(2)lthienyl-trimethine-cyanine iodide.

No. 3 shows a spectrogram of the same emulsion sensitized with bis-[3-ethyl-naphtho-2-1- 4.5-thiazole-(2) l p-thienyl-trimethine cyanine bromide.

No. 4 shows a spectrogram of the same emulsion sensitizied with bis- [3-ethyl-benzselenazo1e-(2) l -thienyl-trimethine-cyanine bromide.

`The following examples serve to illustrate the invention:

Example 1.-A gelatino-silver-bromide emulsion containing about 4 per cent of silver iodide sensitized with bis- [Ii-ethyl-benzoxazole- (2) l- -thienyl-trimethine-cyanine iodide corresponding with the formula imparts to the same a range of sensitiveness extending to a wave length af about 570W. with two maxima, one at about 555W. and the other at about 520ML. The lower limit of the range of 2,060,888 p-tmenyr-trimetnme-mmne bromide ,ememr a thienyi group, Y in both eases stands for sponding with the formula either s V C( R a/-on- CHL-ks oxygen. sulfur or selenium and X stands for a /N N dye precipitating anion. Cim \Br im 2. A photographic material comprising a silver imparts to the same a range of sensitiveness extending to a wave length from about 530W to about '720ml with two maxima, one at about 690W and the other at about 650m.

Example 4.-A gelatino-silver-bromide emulsion containing about 4 per cent of silver iodide sensitized with bis-[3-ethy1-benelenazole-(2).]- p-thienyl-trimethine-cyanine bromide corresponding with the formula B Se i Y imparts to the same a range of sensitiveness extending to a wave length from about 530ml to 690ML with two maxima, one at about 675ML and the other at about 650ML.

What I claim is:

1. A photographic material comprising a silver halide emulsion containing a dyestuff corresponding with the formula wherein `R1 stands for alkyl or aryl, R2 stands for vinylene, phenylene or naphthylene, Rs stands halide emulsion containing a trimethine-cyanine substituted at the central carbon atom oi the trimethenyl chain by a thienyl group.

3. A photographic material comprising a silver halide emulsion containing a bis-[3-aikyl-benzthiazole-(2)ltrimethine cyanine substituted at the central carbon atom by a thienyl group.

4. A photographic material comprising a silver halide emulsion containing a bis-[3-alkyl-benzselenazole-(2)]trimethine cyanine substituted at the central carbon atom by a thienyl group.

5. A photographic material comprising a gelatino-silver-bromide emulsion containing about 4 per cent of silver iodide sensitized with bis-[3- ethyl benzoxazole-(Z) thienyl-trimethinecyanine iodide and having a range of sensitiveness extending to about 570W. with two maxima, one at about 555ML and the other at about 520W.

6. A photographic material comprising a gelatino-silver-bromide emulsion containing about 4 per cent of silver iodide sensitized with bis-[3- ethyl-naphtho 2'.14.5 -thiazole- (2) lthienyl trimethine-cyanine bromide and having a range of sensitiveness extending from about 530ML to about 720ML with two maxima, one at about 690m and the other at about 650ml.

'7. A photographic material comprising a gelatino-silver-bromide emulsion containing about 4 per cent of silver iodide sensitized with bis-[3- ethyl-benzselenazole-(Z) l-'-thienyl-trimethine cyanine bromide and having a range of sensitiveness extending from about 530ML to about 690W. with two maxima, one at about 675ML and the other at about 650ML.

8. A photographic material comprising a silver halide emulsion containing a bis-[B-alkyi-benzoxazole-(Z)l-trimethine-cyanine substituted at the central carbon atom by a thienyi group.

9. A photographic material comprising a silver halide emulsion sensitized with bis-lS-ethylbenzoxazole-(Z thienyltrimethine cyanine iodide.

10. A photographic material comprising a silver halide emulsion sensitized with bis-[B-ethyinaphtho-Z.1'4'.5-thiazole -(2)] ,B thienyl-trimethine-cyanie bromide.

11. A photographic material comprising a sliver halide emulsion sensitized with bis-{3- ethyl-benzselenazole- (2) l--thienyl-trimethine cyanine bromide.

WILHELM SCHNEIDER. 

